Twin mainspring barrel Two barrels in tandem. Lange's twin mainspring barrels allow the implementation of a progressive power-reserve indication and deliver a power reserve of at least three days.

Constant-force escapement A mechanism integrated between the mainspring barrel and the going train in the LANGE 31. It assures constant torque delivery for an entire month and thus enhances the movement’s rate accuracy. A pretensioned, so-called remontoir spring is retensioned by 60 degrees every ten seconds. During the next ten-second period, it transmits this always constant amount of energy to the going train.

Balance cock Small metal plate screwed to the visible side of the movement. It carries the balance wheel shaft bearing.

Gold chaton The gold setting of a bearing jewel - in Lange watches, chatons are often secured to the three-quarter plate with two or three screws.

Screw balance A balance wheel that has adjustable screws and tiny washers along its rim.

Whiplash precision index adjuster An adjusting device composed of a steel spring in the shape of a swan's neck, a pointer, and a setscrew. The screw is used to adjust the beat, or the timing, of the watch in very small increments.

The L034.1 manufacture movement in the LANGE 31 is a true power pack. In a space with a diameter of 37.3 millimetres and a height of 9.6 millimetres, it stores the energy needed to keep running non-stop for 31 days. Two crucial questions had to be answered by Lange’s calibre engineers: how can so much energy be stored in a movement? And, just as important: how can this energy be delivered in a controlled manner? The energy storage function is handled by the large | twin mainspring barrel – two stacked spring barrels, in fact, with an inside diameter of 25 millimetres. They contain the two mainsprings, each of which is 1,850 millimetres long – five to ten times as long as the springs of conventional mechanical wristwatches. When fully wound, their combined energy is equivalent to more than 3 joules. The torque delivered by the mainspring barrel has its maximum when the spring is fully wound and then declines perceptibly as the spring relaxes. This changes the rate parameters of the movement, especially in watches with large power reserve values. To eliminate this unwanted effect in the LANGE 31, the manufactory’s master watchmakers integrated a | constant-force escapement. The main element of this mechanism is a pretensioned spiral spring that is quickly retightened on the fly at intervals of ten seconds. During the ten seconds that follow, the energy stored in the spring is delivered to the going train in a controlled manner. The torque output is virtually constant and powers the watch uniformly throughout 31 days. Apart from its innovative technology, this movement stands out by virtue of its aesthetic appearance. It showcases everything that makes Lange watchmaking artistry so desirable: attractive traditional elements such as the | screw balance, the | whiplash precision index adjuster on the hand-engraved | balance cock, and three screwed | gold chatons. Not to mention the superb finish of all parts that is so typical for Lange.